1. Field of the Invention
This invention relates to a method for analyzing autoradiograph. 2. Description of the Prior Arts
Autoradiography has been known as a method for obtaining locational information on radioactively labeled substances which are distributed in at least one-dimensional direction to form rows on a support medium.
For instance, the autoradiography comprises the steps of: labeling organism-originating biopolymers such as proteins or nucleic acids with a radioactive element; resolving the radioactively labeled biopolymers, derivatives thereof, cleavage products thereof or synthetic products thereof on a support medium through a resolving process such as gel electrophoresis; placing the support medium and a high-speed X-ray film together in layers for a certain period of time to expose the film; developing said film; obtaining the locational information on the radioactively labeled substances from the developed film; and then performing the identification of the polymeric substances, determination of molecular weight thereof or isolation thereof based on the obtained locational information.
Recently, the autoradiography has been effectively used especially for determining the base sequence of a nucleic acid such as DNA or RNA. Further, the autoradiography has been used as an essential means in the screening of gene wherein a hybridization method such as southern blotting, northern blotting or western blotting is employed.
Japanese Patent provisional Publication No. 59(1984)-83057 and No. 60(1985)-10174 and Japanese Patent Application No. 58(1983)-173393 disclose a radiation image recording and reproducing method using a stimulable phosphor sheet in place of a conventional radiography using a radiosensitive material such as an X-ray film. Said method comprises causing a stimulable phosphor in the stimulable phosphor sheet to absorb radiation energy and exciting the stimulable phosphor with an electromagnetic wave (stimulating rays) such as visible light or infrared rays to release the radiation energy from the phosphor sheet as light emission. This method enables exposure time to be greatly shortened and does not suffer chemical fog which is a problem associated with the conventional radiography. Further, this method has an advantage in that the autoradiograph having locational information on the radioactively labeled substances can be obtained in the form of symbols and/or numerals in addition to a visible image, because the autoradiograph can be stored in the phosphor sheet as the radiation energy and read out as stimulated emission in time sequence.
The analysis of the autoradiograph has been, heretofore, made by a person in such a manner that they have detected the distribution of the radioactively labeled substances on the support medium by observing a visualized autoradiograph with own eyes to obtain the locational information (and further informations such as the identification of the biopolymer, the molecular weight thereof and characteristics thereof based on the locational information) on the specific substances labeled radioactively. For instance, the base sequence of DNA is determined by measuring resolved portions of radioactively labeled base-specific DNA fragments or a mixture thereof with eyes and comparing the resolved portions among resolved rows of the DNA fragments with each other. Accordingly, the analysis of the autoradiograph requires a great deal of work and time.
Further, the locational information obtained by the analysis of the autoradiograph varies depending on the person in charge because of inherent unreliability of visual observation, and the accuracy of the information is limited to a certain extent.
There have been previously proposed some methods for automatically obtaining locational information on the radioactively labeled substances in the form of symbols and/or numerals by converting the autoradiograph having the locational information on the labeled substances distributed in at least one-dimensional direction on a support medium into digital signals and subjecting the digital signals to appropriate signal processing (see, Japanese Patent Provisional Publication No. 59(1984)-126527, No. 59(1984)-126278, etc.). Said digital signals corresponding to the autoradiograph can be obtained by visualizing the autoradiograph on a radiographic film according to the conventional radiography and photoelectrically reading out it by means of reflected light or transmitted light. Alternatively, when a stimulable phosphor sheet is used, said digital signals can be obtained by directly reading out the autoradiograph recorded on the phosphor sheet.